The present invention relates to two roll mills and more particularly the present relates to an apparatus for stripping a solid mass in a strip continuously from a two roll mill.
Heat vulcanizable silicone rubber compositions are well-known. Such compositions generally comprise, as the basic ingredient a diorganopolysiloxane polymers reinforcing fillers such as precipitated silica or fumed silica or extending fillers such as lithopone, titanium dioxide, zinc oxide, iron oxide and so forth. Most commonly there is incorporated in such compositions fillers such as fumed silica or precipitated silica. To the resulting composition there is added process aids to facilitate the incorporation of the filler in the diorganopolysiloxane gum polymer. Examples of such process aids are for instance to be found in the Patents of Martellock, Konkle and Fekete which are U.S. Pat. Nos. 3,464,945, 2,890,188 and 2,954,357, which disclose, for instance, nitrogen functional silanes, silanol functional silanes and alkoxy functional silanes as process aids for heat vulcanizable silicone rubber compositions. Such process aids are incorporated into such compositions for two purposes: first, to facilitate the mixing of the filler into the diorganopolysiloxane gum and second to prevent the composition from structuring. Structuring is the phenomena where an uncured composition having silica filler in a diorganopolysiloxane gum will set up or harden prior to cure upon being stored in the uncured condition. It should be noted that such a process aid as disclosed above alleviates to some extent this structuring condition, but do not eliminate it entirely.
Finally, in the heat vulcanizable silicone rubber composition or heat curable silicone rubber composition there may be incorporated various other additives such as compression set additives, flame-retardant additives such as platinum and carbon black and various other additives. The resulting composition may then be taken and there may be incorporated into it an alkyl peroxide as a catalyst. The resulting composition with the alkyl peroxide as a catalyst such as dicumyl peroxide or benzoyl peroxide in it when heated to temperatures above 150.degree. C. will cure to a silicone elastomer. However, in the absence of the peroxide catalyst being incorporated into the composition and even with the peroxide catalyst in some cases, the composition can be stored in the uncured state with all of the ingredients mixed in it except the catalyst for a substantial period of time, such as from one month to a year without any deleterious effects in the composition. The only deleterious effect that is noted in the composition is the phenomena known as structuring which was explained above. Generally, such structuring will comprise the compositions setting up or hardening in the form in which it is formed prior to storage, such that it is very difficult to form into a different shape. It is desirable to form the composition into certain desired shapes in which it is to be sold to customers.
It is common for the silicone manufacturer to take two or three months from the start of the mixing procedure to the time when the composition is ready to be packaged and shipped to customers. Accordingly during such interval of time, the composition may structure. To eliminate the structuring of such composition, it is common in silicone manufacturing facilities to mill mixed but uncatalyzed heat curable vulcanizable silicone rubber compositions on a two roll mill. Simply, this involves taking 25 pound slabs of the strained and mixed components of the heat vulcanizable silicone rubber composition and putting them on the two roll mill where one roller is traveling faster than the other. The milling of the two roll mill forces the structure composition to achieve a molecular breakdown in the structure mass such that there is obtained as a result of the milling procedure pliable sheets of uncured heat vulcanizable silicone rubber composition. In the past, when sufficient amounts of the uncured heat vulcanizable silicone rubber composition had been placed on the mill so as to completely cover one roll, the entire roller portion of the uncured heat vulcanizable silicone rubber composition would be cut across the entire length of the roll so that the sheet of uncured heat vulcanizable silicone rubber composition could fall by gravity to the ground. This uncured sheet of silicone rubber composition would then be taken and cut to the desired strips and powdered with talc or some other non-stick powder and placed in containers to be shipped to the customer, all of which was done manually. When the customer wanted continuous strips of said uncured heat vulcanizable silicone rubber composition of 1,000 lbs. or more, the practice was to take the cut strips that were produced from the sheet that was taken from the two roll mill, and feed them to an extruder where the extruder would extrude out a continuous strip of 1 inch thick by 3 inches wide, which strip would be taken and talc applied to it so as to improve the non-stickness of the strip. Then the strip would be manually guided into a container so that it could be packaged in amounts of up to 1,200 lbs. for shipment to the customer as was desired. Accordingly, it was highly desirable to be able to have an apparatus which would continuously strip by machinery, in a rapid and efficient manner, a continuous strip of uncured heat vulcanizable silicone rubber composition from a two roll mill, dust said cut strip and have it ready for packaging in containers of up to 1,200 lbs.
Accordingly, it is one object of the present invention to provide for an apparatus for continuously cutting a strip of uncured heat vulcanizable silicone rubber composition from a two roll mill; dust the strip with a non-stick powder and present it for packaging in a container.
It is another object of the present invention to provide an apparatus for continuously cutting a strip of solid material from a two roll mill and present the cut strip for dusting continuously and then packaging it.
It is an additional object of the instant invention to provide an apparatus for continuously cutting a strip of uncured heat vulcanizable silicone rubber composition from a two roll mill and present it continuously into a dusting chamber to be continuously dusted with talc and then passed continuously into a packaging container of any weight that is desired by the customer.
It is still an additional object of the present invention to provide a process for continuously cutting a strip of uncured heat vulcanizable silicone rubber composition from a mass of the composition on the two roll mill and pass continuously the cut strip into a dusting chamber and then dust the strip so that a non-stick powder is allowed to cover the strip and then pass the strip continuously into a package.
It is yet an additional object of the present invention to provide a means for precisely adjusting the distance between the cutting edge of a knife of a stripping machine that is presented to the surface of a two roll mill. These and other objects of the present invention are accomplished by means of the disclosure set forth herein below.